The present invention relates to a thermal transfer type recording apparatus which can print a picture in a plurality of colors, and more particularly to a thermal transfer type recording apparatus which has a plurality of recording heads and is used with an ink sheet having a plurality of color regions.
A thermal transfer type recording apparatus that has a plurality of recording heads and is used with an ink sheet having a plurality of color regions, is used as, for example, a printer, a copy machine or a facsimile machine. This type of recording apparatus can realize a high speed printing as it adopts a plurality of recording heads. Further, in this type recording apparatus, printing of a picture can be performed by conveying an ink sheet slower than a sheet on which a picture is to be printed (hereinafter called print sheet), and thus efficiency of utilization of the ink sheet is improved, resulting in minimizing a running cost for the apparatus.
Such a heat transfer type recording apparatus is suggested in the Japanese Patent Publication No. 3-2675. However, the recording apparatus suggested in the above publication has a relatively large space between recording heads, and this results in a problem in that the overall size of the apparatus becomes large. The reason of this problem will be explained below.
Now supposing that L is an interval between recording heads, S is a length of an ink sheet located between the recording heads, A is a pitch of each color region on the ink sheet in a conveying direction of the ink sheet, Q is a length of picture to be printed on a print sheet in a conveying direction of the print sheet, and a conveying speed of the ink sheet is 1/n (n&gt;1) of a conveying speed of the print sheet. Minimizing the size of the apparatus is restricted by the interval between recording heads L which is determined by the picture length Q and the value n. In the above mentioned recording apparatus, since L is set to S, L=Q/(n-1), and Q=n*A, the interval between recording heads L is automatically determined by Q and n. For example, in case n is fixed to a certain value and it is attempted to obtain a longer length of picture, L becomes large and thus the size of the recording apparatus is increased. Accordingly, in order to increase the length Q without increasing the size of the apparatus, n should be made larger. However, the multi-transfer performance of the ink sheet has to be improved so as to allow for a larger n, and that is a technically difficult matter.
Additionally, in the above mentioned recording apparatus, since the interval L and the picture length Q are proportional to each other, the picture length Q is automatically determined when the value of n and the interval L are fixed. It is therefore not possible to form pictures having a variety of lengths by using one apparatus.
In the mean time, there has been suggested, in the Japanese Laid-Open Patent Application No. 63-11368, a heat-transfer type recording apparatus that eliminates utility efficiency decreases due to existence of space between each color region on an ink sheet. This is achieved by setting a length of each color region in a conveying direction to a length sufficient to form a plurality of pictures. This recording apparatus has only one recording head. If a plurality of recording heads are used in order to attempt increasing of recording speed, the overall size of the recording apparatus becomes extremely large similar to the recording apparatus suggested in the Japanese Patent Publication No. 3-2675.
Further, in the recording apparatus suggested in the Japanese Laid-Open Patent Application No. 63-11368, since each color region has a length sufficient to form a plurality of pictures, the ink sheet is required to be rewound in considerable length. This winding operation causes forming of winkles on the ink sheet and increases a recording time.